Proton Conduction Study in 2D Layered Polyoxovanadoborate Frameworks Based on Two Types of Open-Type {V₁₂B₃₂}...

Area of Science:

• Materials Science
• Inorganic Chemistry
• Supramolecular Chemistry

Background:

• Organic-inorganic hybrid materials offer tunable properties.
• Polyoxovanadoborates are versatile building blocks for functional frameworks.
• Templating agents influence the final structure and properties of hybrid materials.

Purpose of the Study:

• To construct novel polyoxovanadoborate frameworks using transition metal complexes as templates.
• To investigate the structural variations and their impact on properties.
• To evaluate the proton conduction capabilities of the synthesized materials.

Main Methods:

• Solvothermal synthesis of polyoxovanadoborate frameworks.
• Single-crystal X-ray diffraction for structural analysis.
• Two-dimensional correlation infrared spectroscopy (2D-COS-IR) for hydrogen bonding analysis.
• Proton conductivity measurements under varying conditions.

Main Results:

• Two isostructural 2D layered polyoxovanadoborate frameworks were successfully synthesized using Cd(en)2^2+ and Cu(en)2^2+ as templating agents.
• Structural analysis revealed differences in hydrogen bonding, channel dimensions, and porosity due to distinct coordinated transition metal ions.
• Proton conductivity measurements demonstrated significant proton conduction, with one framework exhibiting conductivity up to 1.93 × 10^-2 S cm^-1 at 85 °C and 98% relative humidity.
• Enhanced proton conduction in the material with larger channels was observed, correlating structural features with functional properties.

Conclusions:

• The choice of transition metal templating agent significantly influences the structure and porosity of polyoxovanadoborate frameworks.
• The synthesized frameworks exhibit promising proton conduction properties, making them potential candidates for applications in proton exchange membranes or fuel cells.
• Larger channel dimensions within the framework enhance proton transport efficiency, highlighting a structure-property relationship for optimizing proton conductivity.